agnetic Resonance in
Solids. Electronic Journal.agnetic Resonance in
Solids. Electronic Journal.Abstract: A simple model of the Fermi surface for an interpretation of the conduction electron spin resonance (CESR) results in aluminium is developed. According to the real aluminium Fermi surface 48 small rings with the large amount of the $g$-factor shift are arranged in five layers on the Fermi sphere, as distinct from the random distribution of them in the previous model proposed by Silsbee and Beuneu (SB). The present model reproduce known experimental CESR linewidth dependencies versus the frequency at different temperature region as well as the SB model. Additionally to the SB results the CESR linewidth is found to be independent from the magnetic field direction in the high temperature approximation. In both other cases (intermediate and low temperatures) the $g$-value anisotropy over Fermi surface is predicted to lead to the essential angular CESR linewidth dependence with five peaks. Some applications of the model to various systems with conduction electrons are discussed.
PACS: 76.30.Pk; 71.18.+y
Keywords: conduction electrons, Fermi
surface, spin resonance, aluminium
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Abstract: A new formula for the dynamic spin susceptibility has been analyzed with taking into account the strong electron correlations. The correlations sufficiently modify the Stoner-like factor and as a consequence change the phase diagram of the instability. It is remarkable to note that the instability area moves to the low doping. The possible approximates (lorentzian and gaussian) of the real part of the spin susceptibility have been considered. The behavior of the correlation length with doping and temperature in both cases is discussed.
PACS: 74.25.Jb; 74.72.Bk
Keywords: High-T$_c$ superconductivity,
strongly correlated electronic system, spin susceptibility
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Title: Temperature dependencies of $g$-factors in GdBa$_2$Cu$_3$O$_{6+x}$ crystal.
Abstract: The temperature dependencies of the g - factors in dBa$_2$Cu$_3$O$_{6+x}$ crystal are successfully explained using the suggestion that the big macroscopic magnetization of the samples due to the high concentration of Gd$^{3+}$ ions (100 \%) is responsible for the ESR signal. The difference of the temperature behavior of g-factors on the 35 GHz and 9.3 GHz is due to a different fraction of the penetration depth of the field in the superconductor.
PACS: 74.25.Jb; 74.72.Bk
Keywords: high-T$_{c}$ superconductors,
EPR
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Title: NMR Line Shape in Anisotropic Superconductors in Inclined Magnetic Fields
PACS: 74.60.-w; 74.60.Ge
Keywords: high-$T_c$ superconductivity,
nuclear magnetic resonance, vortex lattice
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Abstract: One of the most exciting features of the hole centers $CuO_{4}^{5-}$ in doped cuprates is in their unusually complicated ground state as a result of electronic quasi-degeneracy. An additional hole, doped to the basic $CuO_{4}^{6-}$ cluster with the $b_{1g}$ hole can occupy both the same hybrid $Cu3d-O2p$ orbital state resulting in a Zhang-Rice singlet $^1A_{1g}$ and the purely oxygen $e_u$ molecular orbital resulting in singlet or triplet $ ^{1,3}E_u)$ term with the close energies. We present a detailed analysis of the (pseudo)-Jahn-Teller effect driven by the near-degeneracy within the $^1A_{1g},^{1,3}E_u)$-manifold.
PACS: 71.27.+a, 74.20.s, 74.25.Ha, 76.60.-k
Keywords: cuprates, spin fluctuations,
hyperfine coupling, nuclear resonance
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